You should consult with a lawyer first. The amount of misinformation circulating on the Internet about how AI art is all public domain is enormous. That recent court case (Thaler v. Perlmutter) that made the rounds just recently, for example, does not say what most people seemed to be eagerly assuming it said.

Neither do they have copyright of the stock art they used to purchase. The complete piece, however, including pip boy, is not AI generated. Someone put this together, put effort into it, which easily qualifies it for copyright protection, even if the background is AI generated instead of bought stock art.

If you're talking about that recent legal case, look again. The artist made the claim that the AI was the sole author, but that he should own the IP. I think the vast majority of people would claim that, in it's current state, the AI is a digital tool an author uses to make art. The recent ruling just reconfirm that A machines aren't people, and B you can't just own another author's work.